It is an object of the present invention to provide a jacketing structure which is advantageous for engines of this kind and at the same time is compact, which can be produced and mounted in an economically viable fashion, which does not in any way obstruct the servicing of the engine, and finally ensures an optimum degree of muffling. These objects are achieved in accordance with the present invention by the fact that two carriers of plate form are gripped between the confronting parts of a cylinder housing and the outwardly projecting rims of said carriers constitute a frame which surrounds the engine body from all sides, a plurality of deadening shells conforming to the shape of the engine body bearing in sealed fashion against the same frame with the interposition of at least one vibration deadening insert, and these shells being secured to the body of the engine with the intermediary of spacer elements providing a vibration dampening support.
In the case of internal combustion engines with rows of cylinders arranged in V-formation and a blower which sends cooling air into the gap between the machine body and the jacketing, an advantageous arrangement is achieved by the fact that the sound deadening shell is arranged at each longitudinal side of the rows of cylinders in such a way that the free ends thereof extend to the lower zone of the crank case and defines with the side walls thereof an outlet slot for the cooling air.
A further advantageous form of the invention is achieved by the fact that all free standing outer walls of the crankcase are provided with at least a layer of sound deadening material directly applied thereto, and the two deadening shells arranged along the cylinder rows are equipped at their inner walls with a layer of sound deadening material. By this means a very long sound deadening trajectory or path is defined between the crankcase and the deadening shells, this trajectory reaching to the outlet slot and assisting in the high amount of reduction of the vibrations and noise at the outlet end of the cooling air conduction system of the engine. The deadening layer at the outer walls of the crankcase thus fulfills a second function, namely to reduce the radiation of body noise from these walls.
Another advantageous feature of the invention lies in the fact that the blower is arranged at a narrow side of the engine and the driving shaft of the blower wheel is mounted at the uppermost part in the gap between the V-form cylinder rows, the deadening shell at this side being provided with two inlet ports for cooling air. By this arrangement the cooling air is always inducted at the highest part of the engine so that scarcely any heavy polluted air can be drawn into the system.
It is advantageous in accordance with another feature of the invention that the two inlet ports are provided at their inner walls in each case with a layer of sound deadening material. An optimal effective long deadening run, with a deflection through 90.degree., is provided for in this way at the inlet side of the cooling air conduction system, without calling for any additional installation space.
In engines of the type which have concavity in the crank case for accommodating an externally mounted additional appliance, for example a starter, in an advantageous arrangement the concavity is closed by a cover which is provided with a layer of sound deadening material at its outer wall. By this means the deadening trajectory at the exhaust side of the cooling air conduction system is not retracted in any way by the concavity and therefore does not detrimentally affect the degree of muffling. Moreover, it reduces the radiation of sound from the starter itself.
A further feature of the invention provides that the air filter and the oil cooler are arranged inside the cover at the topmost part of the engine and are exposed directly to the air stream from the blower. Scarcely any grossly polluted air can then be passed to the air filter, and the oil cooler will therefore invariably receive compartively cool air.